The present disclosure relates to industrial process control or monitoring systems. More specifically, the present disclosure relates to process variable transmitters or sensing devices of the type which use wafer or compact style primary sensor elements to measure a process variable of an industrial process.
In industrial settings, control systems are used to monitor and control inventories of industrial and chemical processes, and the like. Typically, the control system that performs these functions uses field devices distributed at key locations in the industrial process and coupled to control circuitry in the control room by a process control loop. The term “field device” refers to any device that performs a function in a distributed control or process monitoring system, including all devices used in the measurement, control and monitoring of industrial processes.
Some field devices include a transducer which couples to the process fluid. A transducer is understood to mean either a device that generates an output signal based on a physical input or that generates a physical output based on an input signal. Typically, a transducer transforms an input into an output having a different form. Types of transducers include various analytical equipment, pressure sensors, thermistors, actuators, solenoids, indicator lights, and others.
Field devices, such as process variable sensors used in industrial processes can be installed in the field on pipelines, tanks and other industrial process equipment. One type of process variable sensor is a flow meter that can measure a rate of fluid flow, for example. One type of flow meter, which employs a differential pressure averaging orifice plate primary element, also referred to as a wafer style primary element, is a popular device for flow measurement in certain environments because its use does not require pipe penetration to be made and the device can easily be inserted into an existing flanged joint. Although this design has been popular at utility measurement points, it has lacked adoption at downstream process measurement points, for example such as in the petroleum industry. One of the key concerns of downstream process piping is exposed bolting. One potential issue is that, when a wafer device is mounted between flanges in process piping and is secured by studs and nuts, the additional length to span the distance of the wafer and sealing gaskets could be a concern and is therefore often not preferred. This additional length is referred to as exposed bolting.
One of the reasons exposed bolting is a concern is the integrity of the piping. Often during startup or shutdown a pipeline may experience a dynamic shock and flanged connections can be possible process leak points. A wafer type device can exacerbate this possibility because the tolerance of the flange bolt holes to stud diameter have more room for the flanges to misalign under these conditions. The greater distance between the flanges the more this misalignment can be pronounced and the greater the chance for a leak to occur at that joint. Another reason exposed bolting is a concern is in the event of a fire, studs would heat up faster than the pipe and expand, reducing pressure on the gasket sealing surface, and losing pressure containment.
The discussion above is merely provided for general background information and is not intended to be used as an aid in determining the scope of the claimed subject matter.